Electronic tuner

Abstract

An electronic tuner of the present invention is arranged such that between an input part of the amplifying circuit and the ground serially connected are a coil and a diode, and a capacitor is connected between the ground and a connecting part between the coil and the diode. The diode is brought into conduction when a voltage supplied from a VHF High control source is at High level, and the coil and input capacitance of the amplifying circuit makes up a gain correction circuit for improving a frequency characteristic of a received signal in a VHF High band. The diode is brought out of conduction when a voltage supplied from a VHF High control source is at Low level, and the coil and the capacitor makes up a trap circuit for improving a frequency characteristic of a received signal in a VHF Low band. This makes it possible to minimize price increase of the apparatus and to improve frequency characteristics in the VHF High band and VHF Low band.

1. An electronic tuner which selectively receives two VHF frequency bands of a VHF High band and a VHF Low band,
 the electronic tuner comprising: 
 an amplifying circuit for amplifying a received signal; and 
 a mixing circuit for mixing the received signal that has been amplified by the amplifying circuit with a local oscillation signal so as to perform frequency conversion, 
 wherein between a ground and at least one of an input part of the amplifying circuit, an output part of the amplifying circuit, and an input part of the mixing circuit serially connected are a coil and a switching element in such a manner that the switching element is arranged on a side of the ground, and a capacitor is connected between the ground and a connecting part of the coil and the switching element, 
 the switching element being brought into conduction when the VHF High band is selected and being brought out of conduction when the VHF Low band is selected. 
 
     
     
       2. The electronic tuner according to  claim 1 , further comprising a power source which generates a band switch control voltage for switching a VHF between the VHF High band and the VHF Low band,
 wherein the switching element is brought into conduction or out of conduction when the band switch control voltage is applied to the switching element. 
 
     
     
       3. The electronic tuner according to  claim 1 , wherein the switching element is a diode. 
     
     
       4. The electronic tuner according to  claim 1 , wherein the switching element is a transistor. 
     
     
       5. An electronic tuner which selectively receives two VHF frequency bands of a VHF High band and a VHF Low band,
 the electronic tuner comprising: 
 a first improvement section for improving a frequency characteristic of a signal in a received VHF High band; 
 a second improvement section for improving a frequency characteristic of a signal in a received VHF Low band; and 
 a switching section for switching between the first improvement section and the second improvement section so that the first improvement section operates when a signal in the VHF High band is received, and the second improvement section operates when a signal in the VHF Low band is received, wherein 
 the first improvement section includes a coil serially connected to the switching section, and 
 the second improvement section includes the coil, and a capacitor which is (i) connected to the coil, (ii) connected in parallel to the switching section. 
 
     
     
       6. The electronic tuner according to  claim 5 , further comprising a power source which generates a band switch control voltage for switching a VHF between the VHF High band and the VHF Low band, wherein the switching section switches between the first improvement section and the second improvement section when the band switch control voltage is applied to the switching section. 
     
     
       7. The electronic tuner according to  claim 5 , wherein the switching section is a diode. 
     
     
       8. The electronic tuner according to  claim 5 , wherein the switching section is a transistor.